A piezoelectric sheet has a characteristic of converting a stress applied thereto into electric power, and devices exploiting this characteristic have been commercially produced in many fields.
A piezoelectric sheet has been applied to an electronic device such as a display device equipped with a touch panel. For example, PTL 1 describes a touch panel provided with a piezoelectric sheet that is adhered to a rear surface of the touch panel. When a press is applied to a front surface of the touch panel, the piezoelectric sheet generates a charge in accordance with the pressure. By detecting the charge, the touch panel is able to measure press information (the intensity of a pressing force).